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RTCWEB architecture Harald Alvestrand. RTCWEB goals. Real Time Communication in the Browser Browser to Browser is Job Number One Usable by JS applications Not (just) for apps we have already deployed Motherhood and Apple Pie Secure Manageable Network Friendly. RTC is not a green field.
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RTCWEB architecture Harald Alvestrand
RTCWEB goals • Real Time Communication in the Browser • Browser to Browser is Job Number One • Usable by JS applications • Not (just) for apps we have already deployed • Motherhood and Apple Pie • Secure • Manageable • Network Friendly
RTC is not a green field • Lots of protocols defined • Code • Knowledge • Hardware • Lots of stuff deployed • Proprietary • Using standard protocols internally • Interoperable
RTCWEB constraints • Browser environment • A few, massively deployed implementations • Scrutiny on code complexity, security, size • Uncontrolled LAN environment • All kinds of middle boxes (NAT, FW, proxy) • No ability to configure local network • Must work with zero configuration
Function layers • Data transport • Data framing and securing • Data formats • Connection management • Presentation and control • Local system support draft-alvestrand-rtcweb-overview
Data transport • IP (obvious) • ICE for establishing desire to communicate • Direct if possible, with TURN relay fallback • UDP if possible, with TCP fallback Controversy: • Whether all of ICE is appropriate • Draft-kaufman-rtcweb-traversal • Congestion control strategies (TFRC?)
Data framing • RTP for media, using RTP/SAVPF profile • RTCP multiplexing, symmetric RTP/RTCP • More details draft-cbran-rtcweb-protocolsdraft-perkins-rtcweb-rtp-usage Controversial: • RTP multiplexing – session-per-media-stream? • Framing of non-media data - UDP/DCCP/DTLS?
Data formats • MTI Codec selection • OPUS (may be uncontroversial) • At least one low-quality “phone” audio codec Controversial: • Video codec status (do not discuss now) • Telephone events (important use case?) • Formats for non-media data
Connection management • Clear requirement to negotiate connections • Legacy has SDP as “lingua franca of descriptions” • SDP has lots of legacy with it • No dominant accepted management protocol • Large SIP installed base – limited interoperability • XMPP has separate following • Simple use cases may be better off on proprietary • Gateway solutions better on browser footprint?
Presentation and Control • User control over his own devices • Management of streams locally • May interact with stream control, but mostly a local matter – may be better addressed in W3C?
Local system support functions • Such as: • Echo cancellation • Automatic gain control • Camera zoom/pan/tilt Some aspects are inter-user and may need standardization.Others are matters of “good citizenship” (“mute when not speaking in large meetings”). For now, leave it for later.
Summary • Consider the environment! • We have lots of things that are obvious • Some of these have implementations • We have a few known controversies • Need to figure out if one alternative has “rough consensus” and move forward • If no rough consensus – what do we need to test? • We will find more controversies over time Rough consensus and running code.